Drying apparatus

ABSTRACT

An upright first conduit has an upper open end, and hot gas with entrained material which is to be dried is passed through the conduit so that it issues from the upper open end into an upwardly closed chamber. A second conduit surrounds the first conduit with clearance and has an upper open end also communicating with the said chamber and located in the region of the level of the open end of the first conduit. A third conduit surrounds the second conduit with clearance and its wall communicates with the wall of the chamber and it serves as the outlet for the hot gases. An arrangement is provided for raising and lowering the level of the upper open end of the second conduit with reference to that of the upper open end of the first conduit to thereby influence the flow conditions in the chamber from the first conduit to the third conduit.

United States Patent 1 Lindemann et al.

[ Jan. 21, 1975 DRYING APPARATUS [75] Inventors: Wilhelm Lindemann,Appelhulsen;

Kurt Riisner, Munster, both of Germany [73] Assignee: Hazemag Dr. E.Andreas KG,

Munster, Germany [22] Filed: July 2, 1973 [21] Appl. No.: 375,924

[30] Foreign Application Priority Data 3,015,390 l/1962 Stewart, Sr.209/140 Primary Examiner-Manuel A. Antonakas Assistant Examiner-WilliamC. Anderson Attorney, Agent, or Firm-Michael S. Striker [57] ABSTRACT Anupright first conduit has an upper open end, and hot gas with entrainedmaterial which is to be dried is passed through the conduit so that itissues from the upper open end into an upwardly closcd chamber. A secondconduit surrounds the first conduit with clearance and has an upper openend also communicating with the said chamber and located in the regionof the level of the open end of the first conduit. A third conduitsurrounds the second conduit with clearance and its wall communicateswith the wall of the chamber and it serves as the outlet for the hotgases. An arrangement is provided for raising and lowering the level ofthe upper open end of the second conduit with reference to that of theupper open end of the first conduit to thereby influence the flowconditions in the chamber from the first conduit to the third conduit.

6 Claims, 2 Drawing Figures FATENTED 5 3,861,059

SHEET 10F 2 I My] DRYING APPARATUS BACKGROUND OF THE INVENTION Thepresent invention relates generally to a drying apparatus, and moreparticularly to an apparatus for entraining and drying particulatematerials.

It is already known to provide various types of drying apparatuseswherein materials are entrained by a stream of hot gas and dried as theyare conveyed by the gas. They utilize an upright conduit through whichthe gas and entrained material are advanced in upward direction, so asto issue from an upper open end of this conduit. They enter from theupper open end into a chamber whose dimensions are larger than those ofthe conduit and in which the coarser and therefore as yet insufficientlydried particles -become separated from the finer and sufficiently driedparticles. These coarser particles can then be recirculated andsubjected to the drying action again, if desired.

In some of the prior-art apparatuses of this type, the separation of thecoarser and finer (not yet properly dried, and already dried) particlestakes place after the gas carrying the particles has been deflected uponissuing from the upper open end of the upright conduit only to one side.However, it has been found that this type of apparatus does not providefor a desired separation efficiency, because due to previous deflectionsthe gas which passes through the upright conduit is given a whirling orrotary motion which it has as it issues from the upper open end of theconduit. The additional onesided deflection imparted to this gas streamand the en trained particles therein, thus creates in the chamber intowhich the gas stream and the particles issue flow conditions whichdisadvantageously influence the separation of dried and as yet undriedparticles.

Another type of prior-art construction utilizes a chamber which is roundand is concentric with reference to the upper open end of the uprightconduit. The separation takes place radially in all directions. Thecoarser particles are separated from the finer particles and the gasstream by venting the finer particles and the gas stream rounddeflecting baffles in upward direction, the intention being that thecoarser particles should descend upon the influence of gravity through acollecting tube which surrounds the upright conduit with clearance. Thisconstruction, however, has the disadvantage that effected by thedeflecting baffles, there will necessarily develope above the upper openend of the upright conduit a gas cushion which disadvantageouslyinfluences the separation of the lighter from the heavier particles.This causes uncontrolled eddies and these, in conjunction with the largeddiameter of the chamber which concentrically surrounds the open end ofthe conduit cause that much dry and fine material is deflected out ofthe intended path and allowed to enter into the outer conduit togetherwith the heavier particles. It is then recirculated into the dryingprocess which will necessarily be disadvantageously influenced in itsefficiency by this fact. Moreover, the thus recirculated already dryfine material can become dried excessively and may actually be damaged.

Still another type of prior-art dryer withdraws the gas stream with boththe fine and coarser particles from the chamber into which it issues outof the upright conduit, in downward direction. The separation takesplace only later, in specific separating devices which, of course,

complicate the construction of the apparatus and increase its expense.

SUMMARY OF THE INVENTION According, it is a general object of thepresent invention to overcome the disadvantages of the prior art.

More particularly, it is an object of the present invention to provide adrying apparatus of the type in question which avoids the aforementioneddisadvantages.

A further object of the invention is to provide such a drying apparatuswhich is highly efficient and inexpensive to construct and maintain.

Another object of the invention is to provide such a drying apparatuswhich is simple in its construction.

In keeping with these objects, and with others which will becomeapparent hereafter, one feature of the invention recites, in anapparatus for entraining and drying fluent materials, in a combinationwhich comprises an upright first conduit having a first upper open endadapted to have hot gas and entrained material to be dried passedtherethrough and out of the open end into an upwardly closed chamber. Asecond conduit surrounds the first conduit with clearance and has asecond upper open end communicating with the chamber in the region ofthe first open end. A third conduit surrounds the second conduit withclearance and its wall communicates with the wall of the chamber and itserves as the outlet for the hot gases. Means is provided for varyingthe level of the second open end with reference to that of the firstopen end, to thereby influence gas and material flow conditions in thechamber.

With this construction, the issuing stream of gas and material forms ineffect a fountain above the upper open end of the upright first conduitwithin the upper open end of the second conduit surpassing the firstconduit and because the varying of the level of the second open endalters the height of the zone or area in which separation of the coarserparticles can take place, the adjustment of the separation of dried fineand still moist coarse particles is greatly improved. The novel featureswhich are considered as characteristic for the invention are set forthin particular in the appended claims. The invention itself, however,both as to its construction and its method of operation, together withadditional objects and advantages thereof, will be best understood fromthe following description of specific embodiments when read inconnection with the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a diagrammatic elevation,showing an embodiment of an apparatus according to the presentinvention; and

FIG. 2 is a diagrammatic fragmentary vertical section, on an enlargedscale, through a detail of FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Discussing the drawing indetail, wherein FIG. 1 shows the complete apparatus and FIG. 2 a detailof the apparatus, it will be seen that reference numeral 1 identifies anupright conduit through which a stream of hot gas produced in the gasgenerator 2 is drawn in upward direction by a ventilator or exhauster 3.Reference numeral 4 identifies a device which admixes the material to bedried, for instance in pulverulent, granular or similar form, with thestream of gas so that it is entrained by the same and advances with thesame in upward direction through the conduit 1. A conduit 5concentrically surrounds the conduit 1 with spacing therefrom, having alower end which can be connected via a gating device 6 with the lowerend of the conduit 1.

A further conduit 7 concentrically surrounds the conduit 5, also withclearance, and has an upper end which is closed (upwardly spaced fromthe upper open ends of the conduits 1 and 5) by means of a hood 8 which,together with the upper end portion of the conduit 7, defines a chamber9. The lower end of the conduit 7 is connected with or merges into aconduit 10 which extends to a separator 11 with which it communicates.

In accordance with the present invention, the upper open end of theconduit 5 is provided with a collar or sleeve 12 which in theillustrated embodiment is configurated as a double-walled element ofsubstantially U- shaped cross-section (see FIG. 2). The collar 12straddles the upper open end of the conduit 5 so that one of its wallsis located outside and its other wall is located inside thecircumferential wall of the conduit 5. Reference numeral 13 identifies atackle (rope or the like) or rod linkage which extends through the hood8 and is connected with the collar 12. The element 13 is onlydiagrammatically illustrated, being well known to those skilled in theart. As indicated by the double-headed arrows in FIGS. 1 and 2, theelement 13 can be used to raise and lower the collar 12 with referenceto the stationary conduit 5 so that in effect the level of the upperopen end of the conduit 5 is made to rise or descend, as the collar 12(which acts as an extension of the upper end portion of the conduit 5)is raised or lowered. The finer and sufficiently dried material enterstogether with the hot gases into the conduit 7, and from there passesvia the conduit 10 into the separator 11 (e.g., a cyclone) wherein it isseparated from its entraining gas to issue through the discharge device14, whereas the gas is vented via the chimney 15 in the direction of theassociated arrow.

The material which is to be dried is admitted via the device 4 and isentrained by the gas stream flowing in the conduit 1, which lifts ittherein. Within the conduit there will be a constant formation of eddieswith the material rising at the center of the conduit 1 and descendingwith reference to the movement of gas at the center along the inner wallof the conduit 1. This significant turbulence causes the individualparticles of material to be contacted again and again with fresh hotgas, so that a rapid heat exchange results in a rapid drying of theparticles. The friction between the particles which is caused by theturbulence, and also between the particles and the wall of the conduit1, and the stresses which develop in the interior of the particles dueto formation of steam, aid in further fragmenting of the particles. Theparticles become lighter as they dry, and also as they become furtherfragmented, and finally issue at the upper open end of the conduit 1into the chamber 9, to enter into the outer conduit 7 and from thereinto the separator 11.

The particles which are not yet sufficiently dried in the conduit 1,will rise at the center of the conduit and exit from the upper open endof the same. Due to the sudden increase of cross-section as the gas andthe particles leave the conduit 1 and enter the space surrounded by theupper end of the conduit 5 formed by the collar 12 the gas flow speedwill drop and the coarser not yet sufficiently dried particles willdescend in the radially outer zone of this space and thus enter into theconduit 5 in which they will drop to the device 6 via which they can bereturned into the conduit 1.

The collar 12 thus constitutes a larger-cross section extension of theconduit 1, in which conditions will develop analogous to those whichobtain in the conduit 1 itself, and these conditions are not as in theprior art influenced by deflecting devices or the like. The stream ofgas widens with its eddies in all directions as it enters from theconduit 1 into the space surrounded by the collar 12, and drops down.The higher the collar 12 is raised, the more the flow speed of the gaswill be reduced and the more coarser and not sufficiently driedparticles of the material to be dried will enter into the conduit 5before the gas stream flows outwardly beyond the upper edge of thecollar 12 and take along the lighter particles. Thus, a very preciseseparation of the particles into finer and coarser or heavier particlesis possible without destroying the formation of a fountain above theupper open end of the conduit 1, which is so important for theefficiency and effectiveness of separation. Moreover, the degree ofseparation can be readily influenced,(i.e., the weight and size of theparticles which are made to enter into the conduit 5 versus those whichare made to enter into the conduit 7 can be varied) by raising orlowering the collar 12.

It will be appreciated that the collar 12 need not have the U-shapedcross section which has been illustrated, but could also be otherwiseconfigurated.

It will be understood that each of the elements described above, or twoor more together, may also find a useful application in other types ofconstructions differing from the type described above.

While the invention as been illustrated and described as embodied in adrying apparatus, it is not intended to be limited to the details shown,since various modifications and structural changes may be made withoutdeparting in any way from the spirit of the present invention.

Without further analysis, the foregoing will so fully reveal the gist ofthe present invention that others can by applying current knowledgereadily adapt it for various applications without omitting featuresthat, from the standpoint of prior art, fairly constitute essentialcharacteristics of the generic or specific aspects of this inventionand, therefore, such adaptations should and are intended to becomprehended within the meaning and range of equivalence of thefollowing claims.

What is claimed as new and desired to be protected by Letters Patent isset forth in the appended claims:

1. In an apparatus for entraining and drying particulate materialsincluding finer and coarser particles, a combination comprising anupright first conduit having a first upper open end and adapted to havehot gas and entrained material to be dried passed therethrough and outof said open end into an upwardly closed chamber; a second conduitsurrounding said first conduit with clearance and having a second upperopen end communicating with said chamber in the region of said firstopen end, and a lower end provided with an outlet for the coarserparticles; a third conduit surrounding said second circuit withclearance and its wall communicating with the wall of said chamber andserving as the outlet in downward direction for said hot gas; and meansfor varying the extent to which the level of said second open end ishigher than the level of said first 6 shaped cross-section, straddlingsaid second open end and having an outer wall surrounding, and aconcentric inner wall received within, said second conduit.

5. A combination as defined in claim 2, wherein said means furthercomprises a tackle for raising and lowering said collar.

6. A combination as defined in claim 2, wherein said means furthercomprises a rod linkage for raising and lowering said collar.

1. In an apparatus for entraining and drying particulate materialsincluding finer and coarser particles, a combination comprising anupright first conduit having a first upper open end and adapted to havehot gas and entrained material to be dried passed therethrough and outof said open end into an upwardly closed chamber; a second conduitsurrounding said first conduit with clearance and having a second upperopen end communicating with said chamber in the region of said firstopen end, and a lower end provided with an outlet for the coarserparticles; a third conduit surrounding said second circuit withclearance and its wall communicating with the wall of said chamber andserving as the outlet in downward direction for said hot gas; and meansfor varying the extent to which the level of said second open end ishigher than the level of said first open end, whereby to influence gasand material flow conditions in said chamber, from the first conduit tothe third conduit.
 2. A combination as defined in claim 1, wherein saidmeans comprises a collar on said second conduit in the region of saidsecond open end and being shiftable upwardly and downwardly withreference to the latter.
 3. A combination as defined in claim 2, whereinsaid collar at least in part surrounds said second conduit.
 4. Acombination as defined in claim 2, wherein said collar is of tubularconfiguration and substantially U-shaped cross-section, straddling saidsecond open end and having an outer wall surrounding, and a concentricinner wall received within, said second conduit.
 5. A combination asdefined in claim 2, wherein said means further comprises a tackle forraising and lowering said collar.
 6. A combination as defined in claim2, wherein said means further comprises a rod linkage for raising andlowering said collar.